The subject matter disclosed herein relates to turbo-machines (e.g., gas and/or steam turbines) and, in particular, to systems and devices that prevent damage to turbo-machines.
Turbines and other turbo-machines may operate under conditions that cause damage. For example, rapid generator unloading can cause acceleration of the turbine shaft or what is known as an over-speed condition in the turbo-machine. In addition to a speed control system, designs for turbo-machines often have a separate protection system to address over-speed conditions. The speed control system has features useful to startup and maintain the turbo-machine in continuous operation. However, when the speed control system does not operate properly or when events or conditions occur outside the ability of the speed control system to control, the over-speed protection system is in place to reduce the likelihood that damage will occur.
Over-speed protection systems for turbo-machines often utilize mechanical devices. Examples of the mechanical devices include spring-loaded eccentric bolts (installed inside the turbine shaft) and spring-loaded pistons (installed outside the turbine shaft). During operation of the turbo-machine, high rotational speed conditions generate centrifugal forces that drive these mechanical devices to strike a lever. This action closes or “trips” a valve or other component, thereby shutting the turbo-machine down. However, although these mechanical devices may provide an effective mechanism for over-speed protection, friction and wear can reduce the reliability of these mechanical devices over time.
Other over-speed protection systems may integrate electronic devices as part of the scheme. In one example, the over-speed protection system includes a solenoid valve. Under normal turbo-machine operation and loading, the solenoid valve is energized to restrain a spring-loaded rod or valve. If the turbo-machine experiences high or rapidly accelerating rotational speed, the solenoid valve is de-energized by the electronic over-speed detection system. This action shuts down the turbo-machine. One problem with these electronic devices is the high solenoid current that is required to compress the spring for resetting the rod or valve. This feature decreases the reliability of the over-speed protection system using these electronic devices.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.